1. Technical Field
The present invention relates to a printer that conveys recording paper through a paper path on which a paper detector is disposed.
2. Related Art
Portable, compact thermal printers are commonly used for printing receipts and labels. Such thermal printers have a paper guide unit that guides the conveyed recording paper to a thermal printhead. When the recording paper is conveyed, static electricity is caused by friction between the recording paper and the paper guide. A photosensor or other type of paper detector is typically disposed to the paper path. If charged recording paper passes near the paper detector, the paper detector can be adversely affected by the effects of static electricity.
Japan Patent 4637597 discloses technology that eliminates static electricity in a paper guide unit. The printer (duplex printing device) disclosed in Japan Patent 4637597 has a pair of left and right adjustable width guides (paper guide unit) that guide the left and right edges of the recording paper. These adjustable width guides are metal, and are disposed movably widthwise to the recording paper. When the gap between the left and right width guides is set to the maximum width, each of the width guides contacts a conductive coil spring on the respective side of the paper path, the width guides are thus grounded through the coil springs, and static electricity is eliminated.
Because the width guides (paper guide unit) are grounded in the configuration taught in Japan Patent 4637597, static electricity in the width guides can be removed and static electricity in the recording paper can be removed through the width guides. Wear resistance can also be assured because the width guides are metal. However, Japan Patent 4637597 is silent about problems in the paper detector caused by static electricity, and providing a member protecting the paper detector from static electricity near the paper detector is not addressed. The paper detector is therefore not sufficiently protected from static electricity, and the paper detector can malfunction due to static electricity.